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First - do you RDP to your Hyper-V Server and use the Hyper-V Manager within this RDP session? If so, do you Logout or Simply disconnect? If you simply disconnect you expose an issue in RDP where the memory consumed in your session is not properly
reclaimed and you end up with false memory consumption readings when you check the management OS. Always logout of your management OS RDP session every so often to clean this up.

okay, that said...

With Dynamic Memory there are a number of things that must align.

Always install / upgrade the Integration Components in the VM.

The Startup Memory - the memory the OS in the VM is allocated at boot time. If the OS in the VM is not dynamic memory aware, this is the RAM it gets, just like static, and depending on the OS in the VM - this can be the number you see when
you check the OS in the VM.

The minimum - this is an idle state that the VM can dip down to, so a VM that is essentially idle can consume no more RAM than is necessary.

the maximum - the most the VM can ever have.

The demand - what the applications in the OS of the VM (plus the OS itself) is requesting. This is a moment in time it can only be 0 or greater. If it at 0 for too long (essentially negative) then RAM is de-allocated.

The buffer - a cushion amount of RAM that is granted to the VM so that the VM always has extra RAM available for the applications to burst in to and use immediately. As the applications can ask for RAM quicker than the hypervisor could respond in giving
it - so the buffer always gives the VM some extra that is beyond what the VM is requesting to handle this.

You should avoid thin provisioning of memory with dynamic memory, ie 4 VMs configured with 32 gb of max ram total when you only have 16 gb, you also have to assume the host needs ram too. You should also resist the temptation of using dynamic ram on exchange
and SQL servers. make sure if you are using dynamic ram you have upper limits property configured.

"You should avoid thin provisioning of memory with dynamic memory, ie 4 VMs configured with 32 gb of max ram total when you only have 16 gb"

Do you have experience or documentation to back this up? I have never seen anything like this from Microsoft. In fact, when you create a VM with dynamic memory, the default max is 1 TB - more than any physical machine I have ever worked on.
I've been using dynamic memory since it first came out, and I have never seen an issue with using the default on several VMs running on a single host.

The opposite is true - one should never try to configure a minimum memory requirement that is more than what is available. But even there, Hyper-V will simply not start a VM if it cannot reserve memory on startup. And, by default, Hyper-V reserves
memory for itself that it will never give to VMs.

Totally agree on the SQL and Exchange memory configurations. There one should make the determination of what is the amount of memory that makes sense for running in their environment and then make it a fixed memory VM.

The maximal memory value is you want split to the child vm biggest “percent” of your total memory. But if you use the dynamic memory the child vm will use its really needs
physical memory ( You can see in the VMM), but that vm use the really physical memory value will limited between the minimum and the maximal value you set.

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